Cargo containers are frequently subject to inspection at seaports, and screened for contraband goods or articles of terrorism. One common inspection modality uses X-rays, or other penetrating radiation, to traverse the cargo containers and provide images of the contents of the containers. Prior art systems for inspecting cargo containers using X-rays have employed one of two modalities: In one scenario, the cargo containers are borne on a truck or other engine-propelled conveyance and moved relative to a scanning portal (either free-standing or truck-borne) or gantry in order for X-rays to penetrate the entire height of the containers and be detected in transmission. (Relative motion may be achieved either by moving the cargo relative to a fixed portal, or, equivalently, by moving a gantry relative to a fixed object of inspection.) Alternatively, a truck with a gantry may be moved in an inspection path relative to one or more fixed cargo containers.
An example of a prior art cargo inspection system that is permanently installed is shown in FIG. 1. Cargo containers 10 must be loaded onto a truck 12 and driven through a fixed gantry 14 where X-rays, or other penetrating radiation, derived from a source located in source enclosure 16, is transmitted through the cargo and detected by detectors (not shown) located within the gantry.
A deficiency of the prior art permanent inspection installation depicted in FIG. 1 is that cargo containers 10, to be inspected, must be hauled to a single scanner location. Changes in port layout or flow of commerce may require reinstallation of the entire system which may be very costly and time-consuming.
It would thus be advantageous to inspect cargo containers without the ponderous set-up overhead entailed in erecting and aligning a cargo scanning gantry, and without requiring that containers be trucked through a portal.